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Black Hat 2024: Secure Shells in Shambles [pdf]

101 points by hdmoore 2y ago

hdmoore 2y ago
The Secure Shell (SSH) protocol has survived as an internet-facing management protocol for almost 30 years. Over the decades it has transformed from a single patented codebase to a multitude of implementations available on nearly every operating system and network-connected device. This presentation dives deep into the Secure Shell protocol, its popular implementations, what's changed, what hasn't, and how this leads to unexpected vulnerabilities and novel attacks. An open source tool, dubbed "sshamble", will be demonstrated, which reproduces these attacks and opens the door for further research. https://github.com/runZeroInc/sshamble https://github.com/runZeroInc/sshamble
- mkj 2y ago
  I didn't realise the old ssh.com codebase was patented, apart from crypto patents like RSA (or IDEA?)
  - throw0101d 2y ago
    See perhaps: * https://www.ssh.com/legal/patents/ https://www.ssh.com/legal/patents/ * https://patents.justia.com/assignee/ssh-communications-security-corp https://patents.justia.com/assignee/ssh-communications-secur...
    - mkj 2y ago
      Those are all dated after the OpenSSH fork
transpute 2y ago
SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to connect to services such as SSH in order to make the exploitation of vulnerabilities (both 0-day and unpatched code) more difficult.
- jcynix 2y ago
  Every now and then I use GnuPG encrypted emails (or a web form) to my servers to open the firewall for certain IP addresses. If the server can decrypt such a message it can safely act on it. The server's default is to only allow certain network ranges to access certain ports, e.g. from my local providers or employers networks.
  - anotherhue 2y ago
    Doesn’t wireguard solve the same issue? Crypto key packet authentication?
    - nwellinghoff 2y ago
      Same question. Can someone chime in on how deploying this would be different from putting ssh behind wiregaurd? On first glance it looks like if you were ultra paranoid you could put this in front of wiregaurd and not even have to open up a udp port? Would that be an advantage to add a layer to secure wiregaurd against 0day?
    - jcynix 2y ago
      > Doesn’t wireguard solve the same issue? Presumably, but my solution is quite a bit older and just a poor man's hack from about 20 years ago ...
  - g_p 2y ago
    Presumably you sign the emails rather than encrypt them? Otherwise anyone who knew the public key of the server (which shouldn't be presumed secret) could send an encrypted instruction, and it would be acted upon, and past encrypted instructions could be replayed.
    - jcynix 2y ago
      > Presumably you sign the emails rather than encrypt them? That's correct, encrypted and signed. Replaying wouldn't be easy because the payload contains a timestamp. The main purpose was to limit the networks which can attempt to connect to ssh and still allow me to have a fallback if I'd happen to be outside of the "usual" network ranges.
tzury 2y ago
a lot to grasp in this one. anyone know if a video is available ?
- baby_souffle 2y ago
  Usually will be in the weeks or months after. I don’t know what the reasons are for the variance though. If you use YouTube, subscribing there should get you notified when defcon starts releasing them all.
mrbluecoat 2y ago
> Tons of issues in the periphery I wonder how TinySSH[1] compares [1] https://github.com/janmojzis/tinyssh https://github.com/janmojzis/tinyssh
metadat 2y ago
What is the fancy htop-like program displayed on page 44? It reminds me of the DeLorean dashboard in Back To The Future :)
- ffsm8 2y ago
  Reading your comment I was putting my money on a customized glances - but after checking the slide... Nope, that's just the default view for btop++ (first screenshot in the link) https://github.com/aristocratos/btop https://github.com/aristocratos/btop
  - metadat 2y ago
    Wow, thank you so much for showing me this. I'll check out glances, too. Any other badass TUI dashboards out there? I wish there were a way to expose these as webpages.
    - ffsm8 2y ago
      Glances can be started in server mode/exposed as website https://glances.readthedocs.io/en/latest/quickstart.html#web-server-mode https://glances.readthedocs.io/en/latest/quickstart.html#web... Wrt other CLI apps: the only way to find out about them is to randomly explore, check out projects. I.e. take anything from here https://github.com/agarrharr/awesome-cli-apps https://github.com/agarrharr/awesome-cli-apps Most people call that procrastinating though ◉ ‿ ◉
      - metadat 2y ago
        ;) thanks for making my day ffsm8, cheers.
    - deleted 2y ago
      [deleted]
- ndegruchy 2y ago
  It looks like btop. One of my favorites.
davidfiala 2y ago
Great presentation. As the founder of teclada.com, I'll also share that one of the biggest risks is not even technical but human: - not managing your SSH keys properly - not even knowing where they are - reuse, copying, etc - forgotten placement of keys in authorized_keys And worst of all: - "no way I'm going to even consider changing any of it" - "our audit logs are .bash_history" ¯\_(ツ)_/¯

101 points by hdmoore 2y ago

The Secure Shell (SSH) protocol has survived as an internet-facing management protocol for almost 30 years. Over the decades it has transformed from a single patented codebase to a multitude of implementations available on nearly every operating system and network-connected device. This presentation dives deep into the Secure Shell protocol, its popular implementations, what's changed, what hasn't, and how this leads to unexpected vulnerabilities and novel attacks. An open source tool, dubbed "sshamble", will be demonstrated, which reproduces these attacks and opens the door for further research. https://github.com/runZeroInc/sshamble https://github.com/runZeroInc/sshamble

mkj 2y ago
I didn't realise the old ssh.com codebase was patented, apart from crypto patents like RSA (or IDEA?)
- throw0101d 2y ago
  See perhaps: * https://www.ssh.com/legal/patents/ https://www.ssh.com/legal/patents/ * https://patents.justia.com/assignee/ssh-communications-security-corp https://patents.justia.com/assignee/ssh-communications-secur...
  - mkj 2y ago
    Those are all dated after the OpenSSH fork

transpute 2y ago

SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to connect to services such as SSH in order to make the exploitation of vulnerabilities (both 0-day and unpatched code) more difficult.

jcynix 2y ago
Every now and then I use GnuPG encrypted emails (or a web form) to my servers to open the firewall for certain IP addresses. If the server can decrypt such a message it can safely act on it. The server's default is to only allow certain network ranges to access certain ports, e.g. from my local providers or employers networks.
- anotherhue 2y ago
  Doesn’t wireguard solve the same issue? Crypto key packet authentication?
  - nwellinghoff 2y ago
    Same question. Can someone chime in on how deploying this would be different from putting ssh behind wiregaurd? On first glance it looks like if you were ultra paranoid you could put this in front of wiregaurd and not even have to open up a udp port? Would that be an advantage to add a layer to secure wiregaurd against 0day?
  - jcynix 2y ago
    > Doesn’t wireguard solve the same issue? Presumably, but my solution is quite a bit older and just a poor man's hack from about 20 years ago ...
- g_p 2y ago
  Presumably you sign the emails rather than encrypt them? Otherwise anyone who knew the public key of the server (which shouldn't be presumed secret) could send an encrypted instruction, and it would be acted upon, and past encrypted instructions could be replayed.
  - jcynix 2y ago
    > Presumably you sign the emails rather than encrypt them? That's correct, encrypted and signed. Replaying wouldn't be easy because the payload contains a timestamp. The main purpose was to limit the networks which can attempt to connect to ssh and still allow me to have a fallback if I'd happen to be outside of the "usual" network ranges.

tzury 2y ago

a lot to grasp in this one. anyone know if a video is available ?

baby_souffle 2y ago
Usually will be in the weeks or months after. I don’t know what the reasons are for the variance though. If you use YouTube, subscribing there should get you notified when defcon starts releasing them all.

mrbluecoat 2y ago

> Tons of issues in the periphery I wonder how TinySSH[1] compares [1] https://github.com/janmojzis/tinyssh https://github.com/janmojzis/tinyssh

metadat 2y ago

What is the fancy htop-like program displayed on page 44? It reminds me of the DeLorean dashboard in Back To The Future :)

ffsm8 2y ago
Reading your comment I was putting my money on a customized glances - but after checking the slide... Nope, that's just the default view for btop++ (first screenshot in the link) https://github.com/aristocratos/btop https://github.com/aristocratos/btop
- metadat 2y ago
  Wow, thank you so much for showing me this. I'll check out glances, too. Any other badass TUI dashboards out there? I wish there were a way to expose these as webpages.
  - ffsm8 2y ago
    Glances can be started in server mode/exposed as website https://glances.readthedocs.io/en/latest/quickstart.html#web-server-mode https://glances.readthedocs.io/en/latest/quickstart.html#web... Wrt other CLI apps: the only way to find out about them is to randomly explore, check out projects. I.e. take anything from here https://github.com/agarrharr/awesome-cli-apps https://github.com/agarrharr/awesome-cli-apps Most people call that procrastinating though ◉ ‿ ◉
    - metadat 2y ago
      ;) thanks for making my day ffsm8, cheers.
  - deleted 2y ago
    [deleted]
ndegruchy 2y ago
It looks like btop. One of my favorites.

davidfiala 2y ago

Great presentation. As the founder of teclada.com, I'll also share that one of the biggest risks is not even technical but human: - not managing your SSH keys properly - not even knowing where they are - reuse, copying, etc - forgotten placement of keys in authorized_keys And worst of all: - "no way I'm going to even consider changing any of it" - "our audit logs are .bash_history" ¯\_(ツ)_/¯